.\" -*- nroff -*-
.\" Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
.\" This file may be copied under the terms of the GNU Public License, v2.
.\"
.TH llverdev 8 "2008 Mar 15" Lustre "configuration utilities"
.SH NAME
llverdev - verify a block device is functioning properly over its full size
.SH SYNOPSIS
.BI llverdev
.RB [ -c
.IR chunksize ]
.RB [ -f "] [" -h ]
.RB [ -o
.IR offset_kb ]
.RB [ -l "] [" -p "] [" -r ]
.RB [ -s
.IR size_mb ]
.RB [ -t
.IR timestamp ]
.RB [ -v "] [" -w ]
.I device
.SH DESCRIPTION
Sometimes kernel drivers or hardware devices have bugs that prevent them from
accessing the full device size correctly, or possibly have bad sectors on disk
or other problems which prevent proper data storage.  There are often defects
associated with major system boundaries such as 2^32 bytes, 2^31 sectors,
2^31 blocks, 2^32 blocks, etc.
.PP
The
.B llverdev
tool will write and verify a unique test pattern across the entire device in
order to ensure that not only is data accessible after it was written, but
also that data written to one part of the disk is not overwriting data on
another part of the disk.
.PP
It is expected that llverdev tool will be run on large size devices (TB), 
so it is always better to run llverdev tool in verbose mode, so that one
can easily restart device testing from the point at which it had stopped. 
.PP
Running a full verification can be time consuming for very large devices,
so it is advisable to start with a partial verification to ensure the
device is minimally sane before investing the time in a full verification.
.SH OPTIONS
.TP
.BR -c | --chunksize " \fIchunk_mb"
IO chunk size in megabytes (default=1), with optional KMG suffix.
.TP
.BR -f | --force
force test to run without confirmation that the device will be overwritten
and all data therein will be permanently destroyed.
.TP
.BR -h | --help
display a brief help message.
.TP
.BR -l | --long
Run a full check, writing and then reading and verifying every block on the
disk.
.TP
.BR -o | --offset " \fIoffset_kb"
offset of IO start in kilobytes (default=0), with optional KMGTP suffix.
.TP
.BR -p | --partial
Run a partial check, only doing periodic checks across the device (1GB steps).
.TP
.BR -r | --read
Run test in read (verify) mode only, after having run the test in
.B -w
mode previously.
.TP
.BR -s | --size " \fIsize_mb"
device or file size in megabytes to use for the test, with optional KMGTP
suffix.  If unspecified, use the actual device or file size (or write until
an error is hit if 0).
.TP
.BR -t | --timestamp " \fItimestamp"
Set test start time as printed at the start of a previously interrupted test
to ensure that the validation data is the same across the whole filesystem
(default=current time())
.TP
.BR -v | --verbose
Run test in verbose mode, listing each read and write operation.
.TP
.BR -w | --write
Run test in write (test-pattern) mode (default run both read and write)
.SH EXAMPLES
.TP
Run a partial device verification on \fB/dev/sda\fR:
.B llverdev -v -p /dev/sda
.br
llverdev: permanently overwrite all data on /dev/sda (yes/no)? y
.br
llverdev: /dev/sda is 4398046511104 bytes (4096.0 GB) in size
.br
Timestamp: 1009839028
.br
Current write offset:        4096 kB
.TP
Continue an interrupted verification at offset \fB4096\fRkB from the start of the device, using the same timestamp as the previous run:
.B llverdev -f -v -p --offset=4096 --timestamp=1009839028 /dev/sda
.br
llverdev: /dev/sda is 4398046511104 bytes (4096.0 GB) in size
.br
Timestamp: 1009839028
.br
write complete
.br
read complete
.SH SEE ALSO
.BR llverfs (8)
